And just bare in mind the fuel economy - The M3 will guzzle, no matter how you drive it - My old V8 RS4, even driving at 60mph, would barely scrape high twentys, a Golf R will hit 40 - But do you buy this sort of car for economy........
If you go M3 get the updated sat nav model, I think 2012 onwards, it makes a massive difference. The M3 is also a £50k plus car and will have £50k running costs